1. Field of the Invention
This invention relates to a multiple deck trommel screen, and more particularly to a multiple deck trommel screen for use in separating fine particles emerging from the end of a rotary drum dryer.
2. Description of the Prior Art
Rotary screen separators for separating fines from larger particulate material is well known. For example, in U.S. Pat. No. 1,182,680 to Hemings, a rotary chip screen is provided having an inner course screen section and an outer fine screen section for separating fine material from larger chips. U.S. Pat. No. 1,596,428 to Greene discloses a dryer and separator for sand and the like, having concentric screens arranged with the inner screens being more course than the outer screens for selective separation of material by size. Other rotary screening devices are shown in U.S. Pat. No. 1,819,049 to Weimer, and in U.S. Pat. No. 3,073,449 to Johanningmeier.
A disadvantage with most prior art devices is overloading of the outer screens whereby the material is not thoroughly mixed so the fines can sift past the larger material to the outer surface to pass through the screen. Furthermore, inadequate agitation at the surface of the outer screen also results in many of the fines being blocked from reaching the screen. Furthermore, fine air-borne particles often are carried over the end of the courser screen and into the recepticle for the course material rather than being deflected so as to pass through the screens and into the recepticle for the fines.